Waste heat recovery apparatus for flash smelting furnace

ABSTRACT

According to the present invention, a flash smelting furnace is provided with a radiation boiler for cooling high-dust-content, hot waste gas generated in the furnace down to a relatively low temperature, and an arrangement for utilizing the low temperature waste gas obtained for gaseous conveying drying of fine ore to be charged into the furnace.

United States Patent Inventors Kazuo Tonooka;

Kazuo Yokomatu, Kamitsuga-gun, Japan Appl. No. 726,339 Filed May 3, 1968 Patented Jan. 12, 1971 Assignee Furultawa Mining Co., Ltd.

Tokyo, Japan Priority May 1 l, 1967 Japan 42/29464 WASTE HEAT RECOVERY APPARATUS FOR FLASH SMELTING FURNACE 3 Claims, 1 Drawing Fig.

11.8. CI 266/13, 75/23, 75/74, 75/89, 75/92, 266/24 Int. Cl C22b 15/00 Field of Search 266/9, 10, ll, 13, 20; 263/no search; 75/23, 35, 40, 74, 89, 92

[56] References Cited UNITED STATES PATENTS 1,755,845 4/1930 Snyder 75/92 1,984,727 12/1934 Brown 75/35 2,846,300 8/1958 Wenzel..... 75/92X 3,042,498 7/1962 Norman 266/20X 3,320,049 5/1967 Hendrickson 266/20X 3,384,475 5/1968 Phillips et al. 266/13X Pn'mary Examiner-J. Spencer Overholser Assistant Examiner-John S. Brown AttorneysRalph E. Bucknam, Jesse D. Reingold, Robert R.

Strack and Henry A. Marzullo, .Ir.

ABSTRACT: According to the present invention, a flash smelting furnace is provided with a radiation boiler for cooling high-dust-content, hot waste gas generated in the furnace down to a relatively low temperature, and an arrangement for utilizing the low temperature waste gas obtained for gaseous conveying drying of fine ore to be charged into the furnace.

PATENTFU JAHIZISYI 3,554,515

INVENTORS,

KAZUO TONOOK-A BY KAZUO YOKOMATU AT (SW WASTE HEAT RECOVERY APPARATUS FOR FLASH SMELTING FURNACE This invention relates generally to an apparatus for the recovery of waste heat from flash smelting furnace, and more specifically to an apparatus for cooling the hot waste gas generated in the flash smelting furnace in the radiation chamber of boiler and then utilizing the low temperature waste gas obtained for gaseous conveying drying of fine ore to be charged into the furnace.

In general, flash smelting furnaces are so designed that pulverized copper ore, e.g. copper pyrites and oxygen are blown simultaneously into the furnace and the effective components of the copper ore is instantaneously melted by the resulting heat of the oxidizing reaction. At this time a hot waste gas is exhausted from the furnace, and it has been customary to cool this hot waste gas first in the radiation chamber of a boiler, which is a space surrounded by steam-generating tubes, down to about 700 C. by radiative transfer of the heat from the gas to the tube wall, and then pass the gas already cooled to a relatively low temperature through a convection chamber having a nest of tubes arranged staggeredly or chequeredly thereby cooling the gas by convective heat transfer to the nest of tubes down to about 300 to 350 C. Y

In the interest of recovery of heat, the gas to be discharged out of the boiler should be at a lowest temperature possible. However, at a waste gas temperature of less than 250 C., 50;, of the waste gas generated by smelting of copper ore will be condensed on the surface of tubing in the boiler and will corrode the tube surface. For this reason, the boiler pressure cannot be reduced below 35 ltg./crn. and therefore the waste gas temperature at the boiler output must be kept above 300 C., or a level higher than the saturation temperature of the boiler by about 50 C. The impossibility of cooling the gas below this point is undesirable from the standpoint of the efficiency of waste heat recovery.

Further, because the hot waste gas from flash smelting furnace has a high dust content, the stream of gas which has proceeded from the radiation chamber to the convection chamber inside the boiler collides with the convection tubes in the latter chamber thereby abrading the tubes or depositing the flue dust on the convection tubes with a corresponding increase in the draught resistance.

It is therefore a principal object of the present invention to provide a new, improved waste heat recovery apparatus for flash smelting furnace which eliminates all of the aforesaid disadvantages of the conventional arrangements.

A further object of the invention is to provide a waste heat recovery apparatus for flash smelting furnace in which the conventional low temperature heat-exchanging region of boiler is replaced by a gaseous conveying dryer for fine ore to be charged into the flash smelting furnace.

Another object of the invention is to provide a waste heat recovery apparatus for flash smelting furnace with which the efficiency of heat recovery from waste gas is remarkably increased without any of the aforesaid troubles due to high-dustcontent waste gases, by dint of the gaseous conveying dryer for fine ores which is provided in lieu of the conventional low temperature heat-exchanging region of boiler.

According to the present invention, a waste heat recovery apparatus for flash smelting fumace is provided which comprises a flash smelting furnace, a radiation boiler for cooling the high-dust-content, hot waste gas generated in said furnace down to a relatively low temperature, and an arrangement for utilizing the low temperature waste gas obtained for gaseous conveying drying of the fine ore to be charged into said furnace.

The gaseous conveying dryer in accordance with the invention comprises, for example, a cage mill for pulverizing copper ore into the state of smalls, a duct through which the pulverized ore is carried by the stream of hot gas exhausted from the boiler, in such way that the pulverized ore is dried by the of heat with the hot gas stream as it passes through the duct, and a cyclone connected to the terminating end of the duct for separating the dried fine ore from the wastegas containing the same. I

For a better understanding of these'andother objects and advantages of the present invention,'description will now be made in more detail with reference to the accompanying drawing showing an embodiment thereof.

The single FIG. in the accompanying drawing is a schematic representation of an apparatus embodying the invention.

The apparatus comprises a flash smelting furnace 10 of the type well known in the art and a radiation boiler 11 in communication with the furnace and which is provided with a high temperature heat-exchanging region. A cage mill 12 of conventional design is provided with a hopper 13 for feeding thereinto a wet ore such as copper pyrites to be pulverized and is communicated with a duct 14 to the boiler 11. A duct 15 serves to carry the ore pulverized atthe cage mill 12 on a gas stream and extends from the cage mill- 12 up to a tangential inlet of a cyclone 16, which is communicated to the furnace 10 via line 17 so that fine ore in the gas stream can be collected by the cyclone and then charged into the top portion of the furnace from the lower outlet of the cyclone. A duct 18 I serves to guide the waste gas which has been separated in the cyclone l6 and contains very fine ore and flue dust into an electric dust collector 19. A duct 20 serves to incorporate the very fine ore and flue dust collected by the electric dust collector 19 into the fine ore passing through the line 17. A suc-.

tion fan 21 serves to attract the waste gas from the furnace in order that the gas may flow through the system and also to discharge the gas cleaned by the electric dust collector out of the system.

In operation of the apparatus, a high-dust-content waste gas at a high temperature of about l,300 C. which has been produced by the furnace 10 is urged out by the suction of the suction fan 21 into the boiler l 1, and'is cooled to about 500 C. by radiation heat transfer at the high temperature heatexchanging region of the boiler. The cooled waste gas then passes through the duct 14 into the cage mill [2, where it dries material ore, e.g., copper pyrites, charged from the hopper 13 into the cage mill 12 while the ore is being pulverized therein. The pulverized ore is carried on the hot, waste gas stream through the duct 15, during which it is subjected to the drying action of the stream of hot gas. Since the hot gas to be used in the form of a gas stream for drying the ore is a waste furnace gas having a very low oxygen content, there is caused no phenomenon of oxidation or combustion of the copper ore in the course of drying.

Then, the gas which contains the fine ore is led into the cyclone 16, where it is separated from the fine ore, and extremely fine ore and flue dust are carried by the gas into the electric dust collector 19. The extremely fine ore and flue dust is removed by the dust collector 19 from the gas and the latter is cooled to about to C. The fine ore separated by the cyclone is introduced together with the extremely fine ore and flue dust into the top portion of the furnace 10 by way of the line 17. The gas dedusted at the electric dust collector l9 and cooled to the low temperature as above is exhausted out of the system by a fan 21. Thus, it will be noted that the present invention makes it possible to bring a remarkable increase in the efiiciency of heat recovery from waste gas and completely eliminate the various disadvantages to which the convection tubes constituting the low temperature heatexchange region of conventional boiler are subjected, because the high-dust-content waste gas generated in the furnace is utilized, in accordance with the invention, in drying fine ore with the gas stream and thereby, at the same time, the waste gas temperature can be decreased to the range of 100 to 150 Further, ordinary arrangements have been that the gas-exhausting equipment and gaseous-conveying drying equipment are provided independently of each other and have their respective cyclones, electric dust collectors and fans. According to the present invention, these components need not be doubled in number of units but may be provided only one each, thus permitting the simplification of the whole arrangement. i

We claim:

1. Wa'stei heat recovery apparatus comprising a flash smelting furnace producing a hot waste gas of high dust content, a

radiation boiler for cooling said waste gas, a duct for the hot waste gases exhausted from said boiler, cage mill means for pulverizing ore and introducing pulverizedore into said duct whereby the pulverized ore is carried by and dried by said I waste gases in said duct, and a cyclone device connected to said duct downstream of said cage mill means for separating dried fine ore from said waste gases.

dust collector, said last mentioned gas containing extremely fine ore and flue dust, and said cyclone device is further provided with means for charging said extremely fine ore and flue dust removed from the last mentioned gas in'the electric dust collector into said furnace. 

2. Waste heat recovery apparatus according to claim 1 wherein said cyclone device is provided with means for discharging said separated fine ore into said furnace.
 3. Waste heat recovery apparatus according to claim 1 wherein said cyclone device is provided with means for introducing the gas separated from the fine ore into an electric dust collector, said last mentioned gas containing extremely fine ore and flue dust, and said cyclone device is further provided with means for charging said extremely fine ore and flue dust removed from the last mentioned gas in the electric dust collector into said furnace. 